JP2004171169A - Mail filtering method, mail server and mail filtering program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mail filtering method, a mail server and a mail filtering program capable of effectively filtering a, so called, annoying mail. <P>SOLUTION: This filtering method for an electronic mail stored in a mail server comprises: a step where a terminal having filtering conditions associated with the transmission address and return address of an electronic mail requests the header information of an electronic mail stored in the mail server; a step where the terminal receives the header information of the electronic mail stored in the mail server; a step where the terminal decides the received header information of the electronic mail based on a filtering condition; a step where the terminal transmits a filtering instruction based on the decision result to the mail server; and a step where the mail server executes the filtering processing based on the filtering instruction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to filtering of email stored in a mail server.
[0002]
[Prior art]
With the development of electronic mail as a means of exchanging information, unsolicited junk mail such as so-called spam mail and virus mail is increasing. This is because relaying e-mail from the sender to the recipient is based only on the e-mail address specified as the destination, and it is easy to send spam if there is an e-mail address of the destination .
[0003]
FIG. 9 is a block diagram showing an embodiment of a conventional mail server.
The server 100 includes a mail receiving unit 11, a mail storage unit 12, and a mail transmitting unit 13. The server 100 connects to the server 2 and the terminal 30 via a communication network 4 such as the Internet.
The server 2 is a so-called mail server that relays an e-mail transmitted by a sender (not shown) to a recipient to the server 100.
The terminal 30 is a terminal used by the recipient to receive the e-mail addressed to the user stored in the server 100, and includes a mail receiving unit 31.
In relaying an e-mail, the server 100 and the server 2 provide an MTA (Mail Transfer Agent) or an MDA (Mail Delivery Agent) function, and the terminal 30 provides an MUA (Mail User Agent) function.
Note that FIG. 9 illustrates only one server 2 that relays e-mail to server 100, but the number of servers that relay e-mail addressed to a recipient to server 100 is not limited to one. .
[0004]
FIG. 10 is a sequence diagram showing an embodiment in which the server 100 relays the e-mail received from the server 2 to the terminal 30.
The server 100 receives the e-mail from the server 2 (S1), stores the e-mail in the mail storage unit 12 which is a so-called mailbox (S2), and stores the e-mail in response to a request from the recipient (S10). The extracted e-mail is extracted (S11) and transmitted to the terminal 30 (S12).
Here, the e-mail is relayed between the server 100 and the server 2 by, for example, Simple Message Transfer Protocol (SMTP), and between the server 100 and the terminal 30 by, for example, POP3 (Post Office Protocol Version 3). Is done.
In SMTP and POP3, it is not necessary to refer to the transmission address, that is, the “From” field of the header information of the e-mail, and the e-mail is relayed by referring only to the destination address, that is, the “To” field. Note that the header information of the e-mail is specified in RFC (Request For Comments) 2822.
[0005]
As described above, since the electronic mail is relayed only by the destination address, it is necessary to relay the electronic mail based on information other than the destination address in order to eliminate so-called junk mail, that is, perform filtering.
There have been proposals for e-mail filtering.
For example, filtering methods have been proposed, such as limiting the number of e-mails that can be transmitted from the same transmission address, and receiving only e-mails whose transmission addresses have been registered in advance by recipients ( For example, see Patent Document 1.)
In addition, the receiver registers the relationship between the transmission address and the priority in advance, and when receiving the e-mail, confirms the transmission address of the received e-mail, and determines the priority of the e-mail based on the previously registered relation. A method has been proposed in which an e-mail required by a recipient can be easily retrieved by changing the e-mail (for example, see Patent Document 2).
[0006]
[Patent Document 1]
JP 2000-163341 A
[Patent Document 2]
JP-A-11-98177
[0007]
[Problems to be solved by the invention]
As described above, conventionally, a large amount of e-mails transmitted from the same transmission address are filtered, or e-mails from a sender unknown to the recipient are filtered. Was implemented.
However, the “From” field of the e-mail is insufficient for obtaining the effect of filtering because the sender can freely specify an e-mail address completely independent of the sender.
On the other hand, as a result of research conducted by the inventor of the present invention, it has been found that the “From” field of the header information and the “Return-Path” field of the spam mail often do not match. In addition, as a result of an experiment using filtering conditions related to the “From” field and the “Return-Path” field, it was found that the effect of eliminating spam was high.
[0008]
The present invention has been made in view of the above-described conventional circumstances, and has as its object to provide a mail filtering method, a mail server, and a mail filtering program that can effectively filter so-called junk mail. .
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is a filtering method for e-mail stored in a mail server, wherein a terminal having filtering conditions related to an e-mail transmission address and a reply address is stored in the mail server. Requesting header information of the email, a terminal receiving the header information of the stored email from the mail server, and determining the header information of the received email based on the filtering condition. And a step in which the terminal sends a filtering instruction based on the result of the determination to the mail server, and the mail server executes a filtering process based on the filtering instruction.
[0010]
The invention according to claim 2 is characterized in that, in the invention according to claim 1, the filtering condition is that the transmission address of the e-mail and the return address do not match, and the filtering processing is the deletion of the e-mail.
[0011]
According to a third aspect of the present invention, an e-mail transferred via a communication network is received and stored, and the stored e-mail is transmitted to the receiver based on a request from the receiver of the e-mail. A mail server that transmits to the terminal, and has means for executing a filtering process based on a filtering condition related to the transmission address and the return address of the e-mail.
[0012]
According to a fourth aspect of the present invention, in the third aspect of the present invention, the filtering condition is that the transmission address of the e-mail does not match the return address, and the filtering process is to delete the e-mail.
[0013]
According to a fifth aspect of the present invention, in the third or fourth aspect, the filtering condition is provided in a terminal different from the mail server, and means for transmitting e-mail header information to the terminal; Means for receiving a filtering instruction, wherein the filtering process is executed based on the filtering instruction from the terminal.
[0014]
The invention according to claim 6 is the invention according to any one of claims 3 to 5, wherein the filtering instruction is a DELE command of a POP3 command.
[0015]
The invention according to claim 7 is characterized in that, in the invention according to claim 5 or 6, the terminal of the receiver is different from the terminal having the filtering condition.
[0016]
According to the present invention, a computer for instructing the mail server to execute filtering of the stored e-mail is provided with means for storing filtering conditions associated with the transmission address and the return address of the e-mail. Means for acquiring the header information of the e-mail stored in the e-mail, means for determining the header information of the acquired e-mail based on the stored filtering conditions, and means for transmitting a filtering instruction to the mail server based on the result of the determination. It is characterized by functioning.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a mail filtering method, a mail server, and a mail filtering program according to the present invention will be described with reference to the drawings. Note that, in the embodiment described below, the electronic mail stored in the mail server is received before the electronic mail recipient A receives the electronic mail addressed to the receiver A stored in the mail server. A case will be described as an example where an electronic mail whose transmission address and reply address do not match is deleted. That is, the filtering condition is an example in which the transmission address and the reply address do not match, and the filtering process is to delete an e-mail corresponding to the filtering condition.
Here, the e-mail addressed to the recipient A refers to an e-mail in which the e-mail address of the recipient A is specified in the “To” field of the e-mail header information. Further, the transmission address and the reply address indicate the e-mail addresses specified in the “From” field and the “Return-Path” field of the e-mail header information. Further, the deletion of the e-mail indicates that the e-mail is not transmitted to the terminal of the recipient in response to the transmission request of the e-mail received from the recipient.
[0018]
FIG. 1 is a block diagram showing an embodiment of a mail server according to the present invention (hereinafter, referred to as “this server”).
Reference numeral 1 denotes this server, which receives and stores e-mail addressed to the recipient A transferred from the server 2 via the communication network 4, and accumulates the e-mail based on a request from the recipient A. This is a so-called mail server that sends the received e-mail to the terminal 3 of the receiver A. The server 1 is connected to the server 2 and the terminal 3 via a communication network 4.
[0019]
Examples of the communication network 4 include a computer communication network such as the Internet and a LAN. The server 1, server 2, and terminal 3 are connected to a communication network 4 via a communication line such as a dedicated line (not shown), a public switched telephone network (PSTN), a wireless telephone network, a CATV network, or a satellite communication network.
[0020]
The server 1 and the server 2 may be any information processing device that can relay an e-mail via the communication network 4, such as a personal computer.
The terminal 3 may be any information processing device that can receive an electronic mail from the server 1 via the communication network 4. For example, a personal computer or a PDA (Personal Digital Assistant) having a data communication function may be used. And mobile phones.
[0021]
In the terminal 3, a mail filtering program according to the present invention (hereinafter, referred to as "the program") operates together with so-called mail software used for receiving an e-mail from the server 1 so as to operate the terminal 3. By controlling each unit, the mail filtering method according to the present invention (hereinafter, referred to as “the present method”) is realized in cooperation with the present server 1.
[0022]
The server 1 includes a mail receiving unit 11, a mail storage unit 12, a mail transmitting unit 13, and a command processing unit 14.
Here, the mail receiving unit 11, the mail storing unit 12, and the mail transmitting unit 13 are respectively the same as those shown in FIG. That is, the mail receiving unit 11 is a unit that receives the electronic mail transferred from the server 2 via the communication network 4. The mail storage unit 12 is a unit that stores the electronic mail received by the mail receiving unit 11 for each recipient, that is, for each destination address of the electronic mail. The mail transmission unit 13 is a unit that transmits the electronic mail stored in the mail storage unit 12 to the terminal of the recipient A based on a request from the recipient A of the electronic mail.
The server 1 has a command processing unit 14. The command processing unit 14 is a unit that executes a filtering process based on a filtering condition.
Here, the command processing unit 14 provides a function of receiving and processing a POP3 command (STAT, TOP, DELE, etc.) as described later. That is, in order to realize this method, it is sufficient that the server 1 has a function of receiving and processing a POP3 command, that is, a normal MTA function.
The command to be received and processed by the command processing unit 14 is not limited to the POP3 command, but may be a command capable of realizing the present method described later, for example, an IMAP4 (Internet Message Access Protocol version 4) command. Good.
[0023]
The terminal 3 includes a mail receiving unit 31, a determination unit 32, a condition storage unit 33, and a history recording unit 34.
The mail receiving section 31 is the same as that shown in FIG. 9 and is a means for receiving the electronic mail stored in the server 1.
[0024]
The determining unit 32 is a unit that obtains and determines the header information of the electronic mail stored in the server 1 and transmits a filtering instruction based on the result to the server 1.
Here, in order to obtain the header information of the e-mail, for example, a STAT command is input to the server 1 to obtain the total number of e-mails addressed to the recipient A stored in the mail storage unit 12, and the obtained mail is obtained. A parameter is generated from the total number of commands and a TOP command is input to the server 1.
The determination is a process of extracting, from the emails stored in the server 1, an email that meets the filtering condition. In the present embodiment, an e-mail in which the transmission address of the e-mail does not match the reply address, that is, the e-mail in which the “From” field and the “Return-Path” field of the header information do not match is extracted.
The filtering instruction is a process for instructing the server 1 to execute a filtering process. In the present embodiment, a DELE command using the mail number of the e-mail extracted by the determination as a parameter is input to the server 1 for execution.
[0025]
The condition storage unit 33 is a unit that stores filtering conditions. The filtering conditions are stored in the condition storage unit 33 by the receiver A prior to the operation of this program.
[0026]
The history recording unit 34 is a unit that records history information of the filtering process. An example of the history information is information related to an e-mail deleted according to the filtering condition, such as a transmission address, a subject, and a transmission date and time. The recipient A can confirm the deleted e-mail by referring to the history recording unit 34 using a unit (not shown) of the terminal 3. Note that the history recording unit 34 is unnecessary when the history is not referred to.
[0027]
Hereinafter, the method will be described with reference to FIGS. FIG. 2 is a sequence diagram showing an embodiment of the present method. 3 and 4 will be described later.
[0028]
First, the server 1 receives an e-mail from the server 2 using the mail receiving unit 11 (S1), and stores the received e-mail in the mail storage unit 12 (S2).
The electronic mail stored in the mail storage unit 12 is transmitted to the terminal 3 of the receiver A based on a request from the receiver A. That is, the server 1 uses the mail transmission unit 13 to receive a mail transmission request (S10), extracts an e-mail addressed to the recipient A from the mail storage unit 12 (S11), and transmits it to the terminal 3 (S11). S12).
[0029]
Here, the server 1 and the terminal 3 cooperate with each other to perform a filtering process during a period from when the e-mail is accumulated (S2) to a request for e-mail transmission (S10), and the e-mail corresponding to the filtering condition is executed. Is transmitted to the terminal 3.
[0030]
The filtering process will be described with reference to FIG.
When the server 1 receives a request for header information of the electronic mail stored in the mail storage unit 12 from the terminal 3 using the command processing unit 14 (S3), the server 1 refers to the mail storage unit 12 and extracts the header information. Then, the data is transmitted to the terminal 3 (S5).
The terminal 3 receives the header information and makes a determination using the determination unit 32 (S6), outputs the result using means (not shown) (S7), and issues an instruction to delete the electronic mail from the recipient A. Accept.
When the server 1 receives an e-mail deletion request from the terminal 3 using the command processing unit 14 (S8), the server 1 deletes the corresponding e-mail from the mail storage unit 12 (S9).
[0031]
As described above, the filtering process is executed by the server 1 and the terminal 3 in cooperation with each other. That is, the server 1 deletes the e-mail corresponding to the filtering condition from the mail storage unit 12, but specifies the e-mail to be deleted and requests the server 1 to delete on the terminal 3. This is a working program.
[0032]
FIG. 3 is a flowchart showing an embodiment of the present program.
When the program starts, it waits for a certain time to elapse (T1). After a certain period of time, the server 1 requests the server 1 for header information (T2). Examples of the starting point of the certain time include the starting point of the program and the last request for header information. When the header information is received from the server 1 (T3), the filtering condition is read from the condition storage unit 33 (T4), the judgment is performed (T5), and the result is output (T6). After that, it waits for a delete instruction (T7), and when there is a delete instruction, requests the server 1 to delete the electronic mail (T8). When a result indicating that the deletion is completed is received from the server 1 (T9), the deletion history is recorded in the history recording unit 34 (T10). This program repeats the above processes T1 to T10.
The processes of T2, T3, T5, T6, and T8 correspond to the processes of S3, S5, S6, S7, and S8 shown in FIG.
[0033]
As a method of outputting the determination result (T6), for example, a list of the header information of the electronic mail stored in the server 1 is displayed together with the determination result on a screen of a display device (not shown) connected to the terminal 3. FIG. 4 is a schematic diagram illustrating an example of a screen displaying a determination result. On the screen P, the judgment results for the e-mails accumulated in the server 1, that is, relayed to the user from the time when the e-mail was received last time to the time when the header information was obtained are displayed in a table format. , Each row of the table is information on one electronic mail.
[0034]
The screen P indicates that there are five e-mails (No. 1 to 5) stored in the server 1 and three of the five e-mails (No. 2, 3, and 4) correspond to the filtering condition. It indicates that you want to.
In the column of the judgment result on the screen P, the blank indicates that the e-mail does not correspond to the filtering condition, the “x” indicates that the e-mail corresponds to the filtering condition, and the “▲” indicates that the filtering condition is satisfied. This is a symbol indicating that the received e-mail is received without being sent.
On the screen P, in addition to the determination result, all or part of the header information, for example, information such as a subject and a sender are displayed.
Note that, instead of providing the column of the determination result on the screen P, for example, a line related to an email corresponding to the filtering condition may be displayed in a different color.
[0035]
The recipient A checks the screen P and determines whether or not to execute the filtering process. That is, if the filtering process is executed while being displayed on the screen P, the column of the determination result is No. It can be confirmed that the e-mails 3 and 4 are deleted and no longer received.
The filtering instruction, that is, the deletion request, is performed by transmitting the DELE command from the terminal 3 to the server 1 when the receiver A presses the “execute filtering process” button on the screen P. The server 1 receives the DELE command using the command processing unit 14 and deletes the corresponding electronic mail in the mail storage unit 12.
[0036]
When the server 1 receives the mail transmission request (S10), the electronic mail stored in the mail storage unit 12 without being deleted, that is, the electronic mail shown in FIG. The three items 1, 2, and 5 are extracted (S11) and transmitted to the terminal 3 (S12).
[0037]
According to the embodiment described above, the recipient A, prior to receiving the e-mail, among the e-mails stored in the server 1 for which the transmission address and the reply address do not match, Can be deleted after confirmation, so that it is possible to prevent the reception of an e-mail having a high possibility of so-called unsolicited e-mail.
[0038]
In the embodiment described above, the filtering condition is a case where the transmission address does not match the return address. However, the filtering condition is not limited to this in the present invention. That is, for example, even when the transmission address and the reply address do not match, a specific transmission address and a subject (“Subject” field) may not be included in the filtering condition.
In this way, for example, a so-called mailing list (the sending address and the reply address often do not match) that the receiver A desires to receive can be excluded from the filtering process.
Note that a specific transmission address not included in the filtering conditions is stored in the condition storage unit 33, and the present program may be configured so that the determination unit 32 reads such information at the time of determination. In addition, information for identifying an e-mail (corresponding to “▲” in the figure) that corresponds to the filtering conditions shown in FIG. 4 but was excluded from the filtering processing last time, such as a transmission address and a subject, is also used. Similarly, the program may be stored in the condition storage unit 33 so that the determination unit 32 reads the program.
[0039]
Further, in the embodiment described above, the filtering condition is related to the sending address and the reply address of the e-mail. In addition, for example, the presence or absence of the attached file, the type of the message body, or The determination may be made by combining the language of the subject, that is, the “Content-Type” or “Subject” fields of the header information.
In this way, for example, it is possible to prevent the reception of an e-mail having a high possibility of a so-called virus mail, such as "attached file", "message body is in HTML format", and "subject is in English". You can also.
[0040]
Before the recipient A refers to the screen P and executes the filtering process, the recipient A changes the email to be subjected to the filtering process, that is, stops deleting the email corresponding to the filtering condition, or The program may be configured so that an e-mail that does not correspond to the above can be deleted.
[0041]
Further, in the example of FIG. 3, the present program is configured to acquire the header information from the server 1 after a certain period of time has elapsed (T1, T2). Instead, the recipient A may be able to set it arbitrarily.
[0042]
Furthermore, the timing of reading the filtering condition (T4) may be before the determination (T5), for example, before the request for the header information (T2).
[0043]
Furthermore, recording of the deletion history (T10) is not an essential component of the program. Therefore, if the deletion history is not recorded, the history recording unit 34 in the terminal 3 is unnecessary.
[0044]
Furthermore, information about an email that does not satisfy the filtering condition may not be displayed on the screen displayed as the determination result. That is, in the example shown in FIG. It is also possible to display only the three cases 3, 4, and 5, and make the receiver A confirm only the e-mail to be filtered. In this case, for example, the column of the determination result need not be provided.
[0045]
Next, another embodiment of the present invention will be described focusing on differences from the above-described embodiment.
In the embodiment described above, the terminal that executes the program and transmits the filtering instruction to the server 1 is the same as the terminal that receives the e-mail from the server 1. The terminal on which this program operates is different from the terminal that receives e-mail from the server 1.
[0046]
FIG. 5 is a block diagram showing another embodiment of the present server, and FIG. 6 is a sequence diagram showing another embodiment of the present method. The same parts as those in FIGS. I have.
The terminal 5 shown in FIG. 5 is a terminal on which this program operates, and realizes a filtering process in cooperation with the server 1. That is, as shown in FIG. 6, when the server 1 receives a request for the header information of the electronic mail stored in the mail storage unit 12 from the terminal 5 using the command processing unit 14 (S3x), the mail storage unit 12, header information is extracted (S4) and transmitted to the terminal 5 (S5x). The terminal 5 receives the header information and makes a determination using the determination unit 32 (S6x), outputs the result using means (not shown) (S7x), and issues an instruction to delete the electronic mail from the recipient A. Accept. When the server 1 receives an e-mail deletion request from the terminal 5 using the command processing unit 14 (S8x), the server 1 deletes the corresponding e-mail from the mail storage unit 12 (S9).
[0047]
Note that the present program, instead of presenting the determination result to the recipient A and accepting the deletion instruction, immediately sends a filtering instruction to the server 1 for the e-mail corresponding to the filtering condition as a result of the determination. It may be configured to transmit.
By doing so, for example, the receiver A operates the program periodically at the terminal 5 at home before receiving the e-mail at the terminal 30 at the workplace, and the electronic mail stored in the server 1 By instructing the server 1 to perform the mail filtering process, it is possible to prevent the terminal 30 from receiving unsolicited mail or the like.
It is not necessary that the terminal that receives the e-mail and the terminal on which this program operates have a one-to-one relationship. That is, for example, before receiving an e-mail on the terminals of a plurality of employees installed in the company, the program is operated on another terminal installed in the company and the electronic mail addressed to the employees is received. By executing the mail filtering process, it is possible to prevent unsolicited mail and the like from being received at the employee's terminal.
[0048]
Next, still another embodiment of the present invention will be described focusing on differences from the above-described embodiment.
In the embodiment described above, the terminal having the filtering condition is a terminal different from the server 1, that is, the terminal 3 in the example of FIG. 1 and the terminal 5 in the example of FIG. The embodiment is a case where the server itself has a filtering condition.
[0049]
FIG. 7 is a block diagram showing still another embodiment of the present server, and FIG. 8 is a sequence diagram showing still another embodiment of the present method. The same parts as those in FIGS. Are given.
Reference numeral 10 shown in FIG. 7 denotes this server, which includes a determination unit 32, a condition storage unit 33, and a history recording unit 34 in addition to the mail reception unit 11, the mail storage unit 12, the mail transmission unit 13, and the command processing unit 14. Have.
In the present embodiment, the program runs on the server 10 and periodically executes the filtering process on the stored e-mail addressed to the recipient A. That is, as shown in FIG. 8, the determination unit 32 requests the command processing unit 14 for the header information of the electronic mail stored in the mail storage unit 12 (S3y). The command processing unit 14 extracts the header information with reference to the mail storage unit 12 (S4). The determination unit 32 obtains (S5y) the header information extracted by the command processing unit 14 and makes a determination (S6y), and requests the command processing unit 14 to delete an email corresponding to the filtering condition (S8y). The command processing unit 14 deletes the requested electronic mail from the mail storage unit 12 (S9).
[0050]
Note that, instead of acquiring the header information after a certain period of time, the program accumulates the e-mail in the mail accumulation unit 12 and acquires the header information before accepting the request from the recipient A. It may be configured as follows.
In this way, the server 10 can transmit only the e-mail that has been subjected to the filtering process to the recipient A.
[0051]
【The invention's effect】
According to the present invention, prior to receiving an e-mail, of e-mails stored in a mail server, e-mail filtering corresponding to a filtering condition related to a preset sending address and a reply address is performed. By executing the processing, it is possible to prevent the reception of an e-mail having a high possibility of a so-called unsolicited e-mail.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a mail server according to the present invention.
FIG. 2 is a sequence diagram showing an embodiment of a mail filtering method according to the present invention.
FIG. 3 is a flowchart showing an embodiment of a mail filtering program according to the present invention.
FIG. 4 is a schematic diagram showing an example of a screen displaying a filtering condition determination result output by the program.
FIG. 5 is a block diagram showing another embodiment of the mail server according to the present invention.
FIG. 6 is a sequence diagram showing another embodiment of the mail filtering method according to the present invention.
FIG. 7 is a block diagram showing still another embodiment of the mail server according to the present invention.
FIG. 8 is a sequence diagram showing still another embodiment of the mail filtering method according to the present invention.
FIG. 9 is a block diagram showing an embodiment of a conventional mail server.
FIG. 10 is a sequence diagram showing an embodiment of a conventional electronic mail relay.
[Explanation of symbols]
1 mail server
2 server
3 terminal
4 Communication network

Claims (8)

A method of filtering e-mail stored in a mail server,
A terminal having filtering conditions related to an e-mail sending address and a reply address, requesting the mail server for header information of the stored e-mail;
The terminal receiving, from the mail server, header information of the stored electronic mail;
A step in which the terminal determines header information of the received email based on the filtering condition;
The terminal transmitting, to the mail server, a filtering instruction based on a result of the determination;
A step of the mail server executing a filtering process based on the filtering instruction. 2. The mail filtering method according to claim 1, wherein the filtering condition is a case where the transmission address of the e-mail does not match the reply address, and the filtering processing is the deletion of the e-mail. An e-mail that receives and accumulates the e-mail transferred through the communication network, and transmits the stored e-mail to the terminal of the recipient based on a request from the recipient of the e-mail. A server,
A mail server comprising means for executing a filtering process based on a filtering condition associated with an e-mail transmission address and a return address. 4. The mail server according to claim 3, wherein the filtering condition is a case where the transmission address of the e-mail does not match the reply address, and the filtering process is the deletion of the e-mail. Filtering conditions are held by a terminal different from the mail server,
Means for transmitting header information of the e-mail to the terminal,
Means for receiving a filtering instruction from the terminal,
5. The mail server according to claim 3, wherein the filtering process is performed based on a filtering instruction from the terminal. 6. The mail server according to claim 3, wherein the filtering instruction is a DELE command of a POP3 command. 7. The mail server according to claim 5, wherein a terminal of the receiver is different from a terminal having a filtering condition. A computer for instructing the mail server to execute filtering of the accumulated e-mail,
Means for storing filtering conditions associated with the email sending address and the reply address,
Means for acquiring header information of the e-mail stored in the mail server,
Means for determining the header information of the obtained email based on the stored filtering conditions,
A mail filtering program functioning as means for transmitting a filtering instruction to the mail server based on a result of the determination.

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